I passed by a river. I entered it and took a bath in it. When I came out, I had fever. The Messenger of Allah ﷺ was informed about it. He said: Ask AbuThabit to seek refuge in Allah from that I asked: O my Lord, will the spell be useful? He replied: No, the spell is to be used except for the evil eye or a snake bite or a scorpion sting. Abu Dawud said: Humah means the biting of snakes and sting of the poisonous insects.
سَمِعْتُ سَهْلَ بْنَ حُنَيْفٍ يَقُولُ مَرَرْنَا بِسَيْلٍ فَدَخَلْتُ فَاغْتَسَلْتُ فِيهِ فَخَرَجْتُ مَحْمُومًا فَنُمِيَ ذَلِكَ إِلَى رَسُولِ اللَّهِ ﷺ فَقَالَ مُرُوا أَبَا ثَابِتٍ يَتَعَوَّذْ قَالَتْ فَقُلْتُ يَا سَيِّدِي وَالرُّقَى صَالِحَةٌ فَقَالَ لاَ رُقْيَةَ إِلاَّ فِي نَفْسٍ أَوْ حُمَةٍ أَوْ لَدْغَةٍ